Removable tubing stop



July 18, 1961 c. H. MlLLER REMOVABLE TUBING STOP A/Ja Filed Dec. 19, 1957 United States Patent 2,992,683 REMOVABLE TUBING STOP Claude H. Miller, Alice, Tex., assignor to Texaco Inc., a corporation of Delaware Filed Dec. 19, 1957, Ser. No. 703,917 5 Claims. (Cl. 166-206) This invention is generally concerned with a tubing stop. More specifically, the invention concerns a tubing stop for use in deep well tubing such as that employed in oil wells.

During the completion of an oil well, it is often necessary to carry out a swabbing operation in order to start the flow of oil from a given producing zone. When such swabbing operation is carried out, it is most usual to first set a tube stop at the bottom of the well tubing before commencing the swabbing, or pumping operation. Such tube stop is recoverable after the swabbing operation, and is merely employed to catch any parts or tools which may become dislodged within the tubing. The use of such a tube stop is well worthwhile because if the cable employed in the well swabbing operation should break, or for some other reason the swabbing tool should be lost down the tubing, it becomes prohibitive to attempt to recover such a tool once it has fallen out of the bottom of the tubing.

The use of tube stops in accordance with the above general indication, is generally old and well-known. However, the prior tube stops that have been employed are relatively complicated in structure, and most make use of relatively complicated operations and equipment for setting the stop at the bottom of the tubing. For these reasons, the prior tube stops were relatively costly and time consuming in use. For example, in the case of a drilling well, where it is desired to carry out some operation that requires the use of a tube stop, and it is desirable to carry this out before removing the rig, the cost of keeping the rig standing by idle is substantial, so that the time saving in eliminating the use of special equipment and technique is a real advantage.

Consequently, it is an object of this invention to overcome the above-mentioned difiiculties in connection with making use of a tubing stop, such that the time and difficulties involved may be reduced to a bare minimum.

Another object of this invention is to provide a simple, yet reliable tube stop that is settable by merely dropping it through the well tree, after tubing has been set in a well. Such tubing stop may be recovered by the simple expedient of running an overshot tool down the well tubing to latch onto a coupling structure of the tube stop.

Still another object of this invention is to provide a very rugged and reliable tubing stop for use in oil wells or the like, which includes a minimum number of parts in the structure thereof, and in addition, which employs an extremely simple seating collar structure at the bottom of the tubing string.

Briefly, this invention is concerned with a swabbing stop for insertion in well tubing, wherein such tubing includes a landing sub on the lower end of said tubing. The invention comprises a solid elongated cylindrical body that has a maximum outside diameter less than the inside diameter of said tubing in order to allow the stop to pass freely through said tubing. The invention also comprises a coupling member at the top of said body for use in removing said stop after use. The above mentioned tubing sub has an enlarged chamber with an axial length substantially greater than the axial length of any enlargements in said tubing above the sub. This includes the well tree with respect to such enlargements. The said enlarged chamber has a sharp shoulder near the bottom of said sub. The invention also comprises a 2,992,683 Patented July 18, 1961 plurality of axially elongated dog means that are carried by said body and are movable radially relative thereto. It also comprises spring means for biasing said dog means to an extended position. The above mentioned dog means have transverse surfaces at the bottom exposed ends thereof for engaging the said sharp shoulder. The other end of each of said dogs means is tapered to cause retraction of the dog means as said stop is removed up the tubing. The longitudinal exposed surfaces of said dog means are substantially parallel to the axis of said body for a distance that is greater than the axial length of said enlargements above said sub, and less than the axial length of said chamber in said sub. The said body has a smooth cylindrical surface for permitting free passage of fluid in the annular space between said tubing and said body.

The foregoing and other objects and benefits of the invention will appear more fully below in connection with the more detailed description which follows. This more detailed description is illustrated in the drawings in which:

FIG. 1 is a schematic cross sectional view of an oil well illustrating tubing in place therein within the casing, and indicating schematically the presence of a socalled well tree;

FIG. 2 is an enlarged longitudinal view partly in cross section, showing the landing collar with the tubing stop in place therein; and

FIG. 3 is a transverse cross sectional view taken along the lines 33 of FIG. 2 looking in the direction of the arrows.

Referring to FIG. 1, there is schematicallyillustrated an oil well 11 that has been drilled in a section of the earth 12; and that has a lining, such as a casing 13 illustrated set therein. In addition, the well has been completed, in a common manner for many oil wells, wherein there is set within the casing 13 a string of permanent tubing 16, that may be suspended from the top of the well 11 in any conventional manner. In addition, there is schematically illustrated a plurality of valves -17 that are attached at the well head, and make up what is commonly known as the christmas tree or simply the well tree.

At the lower end of the tubing string 16 there is attached a landing sub \18 for receiving the tubing stop in accordance with this invention. Tubing sub 18 may also be referred to as a seating collar. There also may be attached at the lowermost end of sub 18 a short collar 19 for potecting the coupling threads at the lower end of a sub 18.

It will be observed that there is illustrated a wire line 22, that may be constructed in the form of a flexible cable and that has attached thereto, at the lower extremity, an overshot 23. This overshot 23 is schematically illustrated. It may take various different forms, so long at it may accomplish the desired purpose of allowing the overshot member 23 to freely slide outside of a male coupling member 24 that is integrally attached to the upper end of a tubing stop 25 (according to this invention), that is shown in place in the sub 18.

Referring to FIGS. 2 and 3, the details of the structure of tubing stop 25 will become apparent. It is pointed out that there is a solid body 28 which is generally cylindrical in form and which has a somewhat narrowed upper end portion 29 that tapers to a small diameter coupling extension 30. At the upper end of coupling extension 30, there is an enlarged head element 31, that includes a tapered tip portion 32 to provide ready engagement with head 31 by the overshot 23 (FIG. 1).

At the lower portion of tubing stop 25, cylindrical body 28 has a pair of grooves, or trenches 35 and 36 which extend axially along the body 28 and have a con siderable depth, in order to receive and laterally support a pair of elongated dogs 37 and 38.

The body 28 may be constructed of any suitably heavy material such as steel or the like, and dogs 37 and 38 are preferably constructed of tempered, hard and yet tough material such as forged steel or the like.

Dogs 37 and 38 include transverse exposed surfaces 39 and 40 respectively at the lower end of each (when viewed as illustrated in FIG. 2). At the other exposed ends of dogs 37 and 38 there are tapered surfaces 42 and 43 respectively. These act to force the dogs to be retracted radially within their respective trenches 35 and 36, as the tubing stop 25 is withdrawn up the tubing string 16.

Each of the dogs 37 and 38 also includes a pair of non-exposed axial extensions 44, 45 and 46, 47 respectively. There is a ring 50 surrounding extensions 44 and 46 at the lower end of the body 28, in order to retain the dogs in operative position within the body 28. Ring 50 is attached securely to the body 28 in any convenient manner, e.g. by means of a transverse rivet 51 extending through the body 28 and being headed flush with the outer surface of the ring 50. Similarly, at the upper end of the dogs 37 and 38 there is a ring 52 which surrounds axial extension 45 and 47 of the dogs, and which is held securely in place by means of a rivet 53.

Internally situated within the lower portion of body 28, there is a pair of coiled springs 56 and 57 that make contact with the inner surfaces of the dogs 37 and 38 at both ends of each of the springs. Springs 56 and 57 pass through transverse holes 58 and 59, that are located through the narrow central part of the body 2 8 which separates the bottoms of the two grooves or trenches 35 and 36.

At the upper end of the body 28 (when viewed as shown in FIG. 2), there is a guide collar 61 that extends radially outward from the surface of body 28 to provide the same effective diameter as the lower portion thereof where the dogs 37 and 3 8 are located. This guide collar 61 may be attached to the body 28 in any feasible manner, e.g. by means of three set screws 62. Each set screw 62 is located between two of three flat surfaces 63 that are equally spaced around the periphery of collar 61 in order to provide additional passageway for flow of fluid within the tubing 16 around the stop 25. The guide collar 61 acts to prevent any possible jamming of the stop 25 during its descent. Such jamming might otherwise be caused by a lateral rocking of the body 28 of stop 25.

The details of the internal structure of sub 18 are clearly illustrated in FIG. 2. These merely include an enlarged diameter chamber 66 that has an axial length somewhat greater than the long straight exposed surfaces of the dogs 37 and 38. Above this chamber 66 the inside walls of sub 18 taper to a smaller diameter bore 67, which is approximately the same diameter as the inside diameter of the tubing string 16. At the lower end of chamber 66, there is a sharp shoulder 68 which acts in cooperation with the transverse surfaces 39 and 40 of the dogs to provide positive stop action that prevents the tubing stop 25 from continuing below sub 18.

Operation In use, the tubing stop 25 will be merely placed into the top of the well tree, after the valves 17 thereof have been opened. Then, by reason of the fact that the long exposed straight surfaces of the dogs 37 and 38 are of a greater extent than any of the enlargements which will be encountered in well tree 17, or in tubing string 16, the tubing stop 25 will pass freely down under its own weight until it reaches the sub 18. The enlargements which will be found in the tubing string 16, as well as the well tree (valves 17), include the coupling joints (not shown) between sections of the tubing string, and also the enlarged inner chambers of the valves 17. Many of these enlargements have sharp shoulders in connection therewith, e.g. the coupling joints are formed by a collar into which adjacent ends of tube sections are screwed. Therefore it is important to have the outer straight surfaces of the dogs 37 and 38 which normally lie parallel to the axis of the tube bore, long enough to carry across such enlargements.

When the stop 25 has found its way down to sub 18, the elongated chamber 66 in the sub 18 will be encountered, and consequently, the dogs 37 and 38 will be extended radially, or translated outward by the springs 56 and 57. Thus, transverse surfaces 3 9 and 40 will come in contact with the shoulder 68 to arrest further downward movement of the stop 25. Now the stop will remain in place during the swabbing operations and thereafter may be readily recovered by the simple operation of lowering the overshot 23 within tubing string 16 while suspended from the wire line 22, until contact is made with the head 31 of the male coupling structure on stop 25.

The stop 25 may be circulated into place down the tubing string 16 by pumping fluid down the tubing. This might be desirable if the existing fluid in the tubing 16 is dense enough to make the downward progress of the stop 25 under its own weight only, too slow.

It will be clear to anyone skilled in the art that any number of dogs might be employed. However, it is pre ferred to use just two, as shown and described, so as to provide a balanced effect with the number of parts.

While a certain embodiment of the invention has been described above in considerable detail in accordance with the applicable statutes, this is not to be taken as in any way limiting the invention but merely as being descriptive thereof.

It is claimed:

1. A swab stop for insertion in well tubing having sections with the ends thereof coupled together to form enlargements and said tubing being suspended by a well tree including a landing sub on the lower end of said tubing, comprising a solid elongated cylindrical body having a maximum outside diameter less than the inside diameter of said tubing to allow the stop to pass freely through said tubing, a coupling member at the top of said body for use in removing said stop after use, said tubing sub having an enlarged chamber with an axial length substantially greater than the axial length of any enlargements in said tubing above the sub including the well tree, said enlarged chamber having a sharp shoulder near the bottom of said sub, a plurality of axially elongated dog means carried by said body and movable radially relative thereto, spring means for biasing said dog means to an extended position, said dog means having transverse surfaces at the bottom exposed ends thereof for engaging said sharp shoulder, the other end of said dog means being tapered to cause retraction of the dog means as said stop is removed up said tubing, the longitudinal exposed surfaces of said dog means being substantially parallel to the axis of said body for substantially the entire length thereof, said parallel exposed length being a distance greater than the axial length of said enlargements above said sub and less than the axial length of said chamber in said sub, said body having a smooth cylindrical surface for permitting free passage of fluid in the annular space between said tubing and said body.

2. A swab stop for insertion in well tubing having sections with the ends thereof coupled together to form enlargements and said tubing being suspended by a well tree including a landing sub on the lower end of said tubing, comprising a solid elongated cylindrical body having a maximum outside diameter less than the inside diameter of said tubing to allow the stop to pass freely through said tubing, said body having an extended smooth cylindrical reduced diameter upper end for preventing excessive lateral rocking motion when the stop is passing freely down the tubing string, a reduced diameter extension at the top of said smooth upper end including a tapered tip and flange for engagement by a female coupling tool to remove said stop up the tubing string, said tubing sub having an enlarged chamber with an axial length substantially greater than the axial length of any enlargements in said tubing above the sub including the well tree, said enlarged chamber having a sharp shoulder near the bottom of said sub, a plurality of axially elongated dog means carried by said body and movable radially relative thereto, spring means for biasing said dog means to an extended position, said dog means having transverse surfaces at the bottom exposed ends thereof for engaging said sharp shoulder, the other end of said dog means being tapered to cause retraction of the dog means as said stop is removed up said tubing, the longitudinal exposed surfaces of said dog means being substantially parallel to the axis of said body for substantially the entire length thereof, said parallel exposed length being a distance greater than the axial length of said enlargements above said sub and less than the axial length of said chamber in said sub, said body having a smooth cylindrical surface for permitting free passage of fluid in the annular space between said tubing and said body.

3. A swab stop for insertion in well tubing having sections with the ends thereof coupled together to form enlargements and said tubing being suspended by a well tree including a landing sub on the lower end of said tubing, comprising a solid elongated cylindrical body having a maximum outside diameter less than the inside diameter of said tubing to allow the stop to pass freely through said tubing, said body having an extended smooth cylindrical reduced diameter upper end for preventing excessive lateral rocking motion when the stop is passing freely down in the tubing string, said smooth upper end having a guide collar spaced from the lower part of said body and including means for reducing the restriction to fluid flow past the collar, a reduced diameter extension at the top of said smooth upper end including a tapered tip and flange for engagement by a female coupling tool to remove said stop up the tubing string, said tubing sub having an enlarged chamber with an axial length substantially greater than the axial length of any enlargements in said tubing above the sub including the well tree, said enlarged chamber having a sharp shoulder near the bottom of said sub, a plurality of axially elongated dog means carried by said body and movable radially relative thereto, spring means for biasing said dog means to an extended position, said dog means having transverse surfaces at the bottom exposed ends thereof for engaging said sharp shoulder, the other end of said dog means being tapered to cause retraction of the dog means as said stop is removed up said tubing, the longitudinal exposed surfaces of said dog means being substantially parallel to the axis of said body for substantially the entire length thereof, said parallel exposed length being a distance greater than the axial length of said enlargements above said sub and less than the axial length of said chamber in said sub, said body having a smooth cylindrical surface for permitting free passage of fluid in the annular space between said tubing and said body.

4. A swab stop for insertion in well tubing having sections with the ends thereof coupled together to form enlargements and said tubing being suspended by a well tree including a landing sub on the lower end of said tubing, comprising a solid elongated cylindrical body having a maximum outside diameter less than the inside diameter of said tubing to allow the stop to pass freely through said tubing, said body having an extended smooth cylindrical reduced diameter upper end for preventing excessive lateral rocking motion when the stop is passing freely down the tubing string, said smooth upper end having a guide collar spaced from the lower part of said body and including a plurality of flat spots around the periphery of the collar for reducing the restriction to fluid flow past the collar, a reduced diameter extension at the top of said smooth upper end including a tapered tip and flange for engagement by a female coupling tool to remove said stop up the tubing string, said flange having a sharp shoulder substantially at right angles to the axis of the stop at the base of said tapered tip, said tubing sub having an enlarged chamber with an axial length substantially greater than the axial length of any enlargements in said tubing above the sub including the well tree, said enlarged chamber having a sharp shoulder near the bottom of said sub, a plurality of axially elongated dog means carried by said body and movable radially relative thereto, an axially extending trench in said body for receiving each of said dogs, said trenches extending radially to a depth sufficient to permit retraction of each dog flush with the outer cylindrical surface of the body, a plurality of coil springs extending diametrically through the body and contacting the bottom edges of oppositely located pairs of said dogs, said dogs having nonexposed axial extensions, a pair of retaining rings surrounding said axial extensions for preventing ejection of said dogs-by said springs, said dog means having transverse surfaces at the bottom exposed ends thereof for en gaging said sharp shoulder, the other end of said dog means being tapered to cause retraction of the dog means as said stop is removed up said tubing, the longitudinal exposed surfaces of said dog means being substantially parallel to the axis of said body for substantially the entire length thereof, said parallel exposed length being a distance greater than the axial length of said enlarge ments above said sub and less than the axial length of said chamber in said sub, said body having a smooth cylindrical surface for permitting free passage of fluid in the annular space between said tubing and said body.

5. A swab stop for insertion in well tubing having sections with the ends thereof coupled together to form enlargements and said tubing being suspended by a well tree including a landing sub on the lower end of said tubing comprising a solid elongated cylindrical body having a maximum outside diameter less than the inside diameter of said tubing to allow the stop to pass freely through said tubing, said body having an extended smooth cylindrical reduced diameter upper end for preventing excessive lateral rocking motion when the stop is passing freely down the tubing string, said smooth upper end having a guide collar near the top thereof and including three flat spots spaced around the periphery of the collar for reducing the restriction to fluid flow past the collar, said guide collar having the same outside diameter as said body, a reduced diameter extension at the top of said smooth upper end including a tapered tip and flange for engagement by a female coupling tool to remove said stop up the tubing string, said flange having a sharp shoulder substantially at right angles to the axis of the stop at the base of said tapered tip, said tubing sub having anenlarged chamber with an axial length substantially greater than the axial length of any enlargements in said tubing above the sub including the well tree, said enlarged chamber having a sharp shoulder near the bottom of said sub, two axially elongated dogs carried by said body and located diametrically opposite one another, an axially extending trench in said body for receiving each of said dogs, said trenches extending radially to a depth suflicient to permit retraction of each dog flush with the outer cylindrical surface of the body, a pair of coil springs extending diametrically through the body and contacting the inner edges of both said dogs to bias the dogs outward into contact with the Walls of said well tubing, said dogs having non-exposed axial extensions, a pair of retaining rings surrounding said axial extensions for preventing ejection of said dogs by said springs, said dogs having stop surfaces extending at right angles to the axis of the stop at the bottom end of each dog for fluid in the annular space between said tubing and said body.

References Cited in the file of this patent smooth cylindrical surface for permitting free passage of 10 2,960,165

UNITED STATES PATENTS Crowell Mar. 13, Miller Mar. 30, Fredd July 9, Minter et al. Dec. 17, Schramm Nov. 15, 

